PROJECT SUMMARY This project marks a groundbreaking first step to delineating the influence of senescent cells in the pathogenesis of cardiovascular diseases in patients with Marfan syndrome. Affecting 1 in every 5000 live births worldwide, with the multiple highly penetrant cardiac phenotypes (including mitral valve prolapse, aortic valve regurgitation, and aortic aneurysms), Marfan syndrome often leads to multiple major cardiovascular surgeries throughout a patient's life. Though it is clear that mutations in the fibrillin-1 gene and subsequent overactivation of TGF? signaling represent a well-defined molecular origin of Marfan syndrome, development of therapeutic interventions that improve event-free and/or overall survival has been challenging at best. Convention indicates that early onset of multiple cardiovascular diseases in Marfan syndrome resembles a ?progeroid-like? phenotype, and recent reports suggest that many patients develop lipodystrophy and other phenotypes associated with chronological aging. Critically, recent studies by our research group at Mayo (Miller/Kirkland) suggests that accumulation of senescent cells can drive progression of multiple diseases in pre-clinical models of chronological aging and human disease. Thus, our central hypothesis?supported by substantial preliminary data?is that accumulation of senescent cells is a major driver of increased matrix remodeling in Marfan syndrome, and represents a novel molecular mechanism contributing to initiation and progression of multiple pathological cardiovascular phenotypes. Thus, the aims of the current application are: Measure and determine the effects of genetically reducing senescent cell burden on phenotypic progression and molecular underpinnings of aortic, aortic valve, and mitral valve dysfunction in Marfanoid mice; 2) Determine whether pharmacological clearance of senescent cells can attenuate molecular drivers and slow phenotypic progression of aortic, aortic valve, and mitral valve dysfunction in Marfanoid mice, and 3) Determine the distribution and burden of senescent cells in aortic, aortic valve, and mitral valve tissues from humans with Marfan syndrome. We will use a combination of unique in vivo animal models and evaluation of normal and Marfanoid human tissue in this application to conduct key proof-of-concept studies with genetic clearance of senescent cells, translationally-relevant interventions in animals, and key confirmatory studies to bridge to human disease relevance. Collectively, we aim to demonstrate that senescent cells play a significant role in the progression of Marfan-associated cardiovascular disease, with these studies being specifically designed to lay a foundation and justification for pursuit of early clinical trials to address this critical set of diseases in patients with Marfan syndrome.